It's only rock 'n' roll, but a lot of people, including some very big-name celebrities, sure seem to like it. On Friday, May 3, the Rolling Stones celebrated a half-century in the music biz by kicking off their "50 and Counting" tour at Los Angeles's Staples Center, and they were joined--onstage and in the audience--by some very famous guests.

The first surprise guest to sit in with the Stones--though it wasn't a surprise if you'd checked out her giddy Twitter page earlier that afternoon--was No Doubt frontgoddess Gwen Stefani, who sauntered out in a bedazzled lips-logo'd T-shirt, leather leggings, and flat-ironed Cher hair to duet with iconic frontgod Mick Jagger on "Wild Horses." It wasn't a perfect pairing--the song seemed to be in slightly too low a key for Gwen, and she probably would have fared better on a jauntier, dancier Stones number like "Emotional Rescue" or "Miss You." But her starry-eyed enthusiasm was still adorable to behold. (A true fan, she'd also been spotted six days earlier in the audience at the Stones' warm-up gig at L.A.'s 700-capacity Echoplex club.) She really was just a girl…singing onstage with one of the most famous rock stars of all time.

Seemingly equally star-struck was Keith Urban, who joined the Stones for a three-way guitar throwdown on "Respectable," and respectably held his own alongside the band's more famous Keith (Keith Richards, that is--duh). The man looked so happy that at one point he dropped to his knees in worship at Mick's pointy-booted feet; suffice to say, he looked way happier than he has while suffering on the "American Idol" panel lately.

The other exciting guest of the evening was another Mick: Mick Taylor, who was the Stones' guitarist from 1969-74, the fruitful years in between Brian Jones and Ronnie Wood. His epic "Midnight Rambler" jam session alongside Richards and Wood, as Jagger (one of the best male dancers in rock) wailed on harmonica and flailed with abandon, was a highlight of the band's 23-song set.

The audience was star-studded as well: Among the spectators were KISS's Paul Stanley, Pierce Brosnan, Melanie Griffith, and Kelsey Grammer. But none of these people made as grand an entrance as Jack Nicholson, whose well-known Lakers superfandom makes him a regular at the Staples venue. As Jack walked to his usual reserved courtside seat up at the front, right before the concert, the audience whooped and cheered. Later, after Mick apologized for having to move the "50 and Counting" tour kickoff from its originally scheduled May 2 date to accommodate the NBA playoffs, he quipped: "It's either us or the Lakers. So now you got us. But it doesn't matter to Jack Nicholson, because he was coming to both of them!"

The nearly two-and-a-half-hour show started off with a highlight reel that featured a few other familiar faces. As a mini-documentary of fans singing the Stones' praises ran on the Staples' jumbotron, among the higher-profile admirers were Johnny Depp, Martin Scorsese, Iggy Pop, Pete Townshend, Jane's Addiction's Perry Farrell, Nick Cave, the Black Keys' Patrick Carney, and Cate Blanchett, who amusingly said it "really pissed her off" how skinny the Stones were.

And then out bounded the band onto the bulbous, lips-shaped stage, Mick looking as Blanchett-infuriatingly skinny as he did 50 years ago, if not skinnier. A wasp-waisted waif, dressed in form-fitting, mime-like all black, Mick practically looked like he was wearing a corset (or had undergone rib-removal surgery). It soon became apparent how he'd kept off the weight in his "old age"--the man never stopped moving, and even as the crowd grew noticeably fatigued as the clock neared midnight, Mick and the boys (okay, men) were still rocking. Behind them, the jumbotron ran iconic black-and-white photos from the Stones' early-'60s Brian Jones era, and while the contrast between those babyfaced images and the Stones' current-day creased visages was startling at first, soon it just became flat-out impressive that these guys still looked as good as they did, five decades later.

The setlist was packed with the expected crowd-pleasing hits (such are the joys of seeing a heritage act with no new, not-classic album to promote), although there were two extremely pleasant song surprises: 1980's aforementioned disco ditty "Emotional Rescue," which the Stones had never played live before, and the Beggars Banquet cut "Factory Girl," which Mick introduced by saying, "You don't mind us doing songs that aren't that well-known, do you?" Judging from the audience reaction, plenty of people at Staples knew the tune, and no one minded.

Other highlights included two collegiate numbers, an opening brass-instrumental procession of "Satisfaction" by UCLA's marching band and an encore of "You Can't Always Get What You Want" with a choir from Cal State Long Beach; a fiery "Gimme Shelter" duet with backup diva Lisa Fisher; a two-song Keef mini-set of "Before They Make Me Run" and "Happy"; and "Sympathy for the Devil," during which Mick performed in a floor-length cape made out of what appeared to be shaggy black Muppet fur, just to prove he really is a man of wealth and taste.

The concert was sold-out, although at first the Staples Center had trouble filling the venue's pricier ($600!) premium seats--leading the band to issue 1,000 or so much more reasonably priced $85 tickets, some of which were actually located in the "Tongue Pit" right in front of the stage, the day of the show. (Still not as much of a bargain as the $20 tickets for the previous weekend's Echoplex gig, but a good deal nonetheless.) However, it seemed like all of the fans in the arena, regardless of where they were sitting or how much they'd shelled out, felt they'd gotten their money's worth.